1. Technical Field
The present invention relates to a solid-state imaging apparatus, as well as an electronic device and the like that use the solid-state imaging apparatus.
2. Related Art
In a solid-state imaging apparatus such as a contact image sensor, light receiving elements that are each arranged in a different one of pixels in a pixel unit perform photoelectric conversion in accordance with illuminance, and a readout circuit reads out image information from the light receiving elements. An output voltage of the readout circuit is supplied to a CDS (correlated double sampling) circuit so as to cancel out variations in an offset voltage between the plurality of pixels. The CDS circuit generates a pixel signal based on a difference between an output voltage output from the readout circuit at the time of reset and an output voltage output based on the readout of pixel information.
As related art, published U.S. Patent Application No. 2012/0182450 discloses a solid-state imaging apparatus that is intended to improve the precision of temperature measurement based on the current-voltage characteristics of a diode. This solid-state imaging apparatus includes a pixel array unit, an image CDS processor, a temperature sensor, a temperature CDS processor, and a timing generator. As shown in FIG. 5 of published U.S. Patent Application No. 2012/0182450, the image CDS processor includes the following elements on a per-column basis: a capacitor C1, a comparator (operational amplifier) PA, a switch transistor Tcp, an inverter V, and an up/down counter UD.
Solid-state imaging apparatuses are expected to improve the linearity of a signal voltage relative to a change in illuminance, downsize the circuits, and reduce current consumption. However, a CDS circuit composed of operational amplifiers, like the solid-state imaging apparatus of published U.S. Patent Application No. 2012/0182450, has significant disadvantages including an increased circuit area and increased current consumption. There is also the problem of difficulty in detecting a defective portion when the CDS circuit is determined to be defective in an operation test.